xtensa: ISS: fix locking in TAP network adapter

commit 24e94454 upstream.

- don't lock lp->lock in the iss_net_timer for the call of iss_net_poll,
  it will lock it itself;
- invert order of lp->lock and opened_lock acquisition in the
  iss_net_open to make it consistent with iss_net_poll;
- replace spin_lock with spin_lock_bh when acquiring locks used in
  iss_net_timer from non-atomic context;
- replace spin_lock_irqsave with spin_lock_bh in the iss_net_start_xmit
  as the driver doesn't use lp->lock in the hard IRQ context;
- replace __SPIN_LOCK_UNLOCKED(lp.lock) with spin_lock_init, otherwise
  lockdep is unhappy about using non-static key.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

arch/xtensa/platforms/iss/network.c

@@ -349,8 +349,8 @@ static void iss_net_timer(unsigned long priv)
 {
 	struct iss_net_private *lp = (struct iss_net_private *)priv;
 
-	spin_lock(&lp->lock);
 	iss_net_poll();
+	spin_lock(&lp->lock);
 	mod_timer(&lp->timer, jiffies + lp->timer_val);
 	spin_unlock(&lp->lock);
 }
@@ -361,7 +361,7 @@ static int iss_net_open(struct net_device *dev)
 	struct iss_net_private *lp = netdev_priv(dev);
 	int err;
 
-	spin_lock(&lp->lock);
+	spin_lock_bh(&lp->lock);
 
 	err = lp->tp.open(lp);
 	if (err < 0)
@@ -376,9 +376,11 @@ static int iss_net_open(struct net_device *dev)
 	while ((err = iss_net_rx(dev)) > 0)
 		;
 
-	spin_lock(&opened_lock);
+	spin_unlock_bh(&lp->lock);
+	spin_lock_bh(&opened_lock);
 	list_add(&lp->opened_list, &opened);
-	spin_unlock(&opened_lock);
+	spin_unlock_bh(&opened_lock);
+	spin_lock_bh(&lp->lock);
 
 	init_timer(&lp->timer);
 	lp->timer_val = ISS_NET_TIMER_VALUE;
@@ -387,7 +389,7 @@ static int iss_net_open(struct net_device *dev)
 	mod_timer(&lp->timer, jiffies + lp->timer_val);
 
 out:
-	spin_unlock(&lp->lock);
+	spin_unlock_bh(&lp->lock);
 	return err;
 }
 
@@ -395,7 +397,7 @@ static int iss_net_close(struct net_device *dev)
 {
 	struct iss_net_private *lp = netdev_priv(dev);
 	netif_stop_queue(dev);
-	spin_lock(&lp->lock);
+	spin_lock_bh(&lp->lock);
 
 	spin_lock(&opened_lock);
 	list_del(&opened);
@@ -405,18 +407,17 @@ static int iss_net_close(struct net_device *dev)
 
 	lp->tp.close(lp);
 
-	spin_unlock(&lp->lock);
+	spin_unlock_bh(&lp->lock);
 	return 0;
 }
 
 static int iss_net_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct iss_net_private *lp = netdev_priv(dev);
-	unsigned long flags;
 	int len;
 
 	netif_stop_queue(dev);
-	spin_lock_irqsave(&lp->lock, flags);
+	spin_lock_bh(&lp->lock);
 
 	len = lp->tp.write(lp, &skb);
 
@@ -438,7 +439,7 @@ static int iss_net_start_xmit(struct sk_buff *skb, struct net_device *dev)
 		pr_err("%s: %s failed(%d)\n", dev->name, __func__, len);
 	}
 
-	spin_unlock_irqrestore(&lp->lock, flags);
+	spin_unlock_bh(&lp->lock);
 
 	dev_kfree_skb(skb);
 	return NETDEV_TX_OK;
@@ -466,9 +467,9 @@ static int iss_net_set_mac(struct net_device *dev, void *addr)
 
 	if (!is_valid_ether_addr(hwaddr->sa_data))
 		return -EADDRNOTAVAIL;
-	spin_lock(&lp->lock);
+	spin_lock_bh(&lp->lock);
 	memcpy(dev->dev_addr, hwaddr->sa_data, ETH_ALEN);
-	spin_unlock(&lp->lock);
+	spin_unlock_bh(&lp->lock);
 	return 0;
 }
 
@@ -520,11 +521,11 @@ static int iss_net_configure(int index, char *init)
 	*lp = (struct iss_net_private) {
 		.device_list		= LIST_HEAD_INIT(lp->device_list),
 		.opened_list		= LIST_HEAD_INIT(lp->opened_list),
-		.lock			= __SPIN_LOCK_UNLOCKED(lp.lock),
 		.dev			= dev,
 		.index			= index,
-		};
+	};
 
+	spin_lock_init(&lp->lock);
 	/*
 	 * If this name ends up conflicting with an existing registered
 	 * netdevice, that is OK, register_netdev{,ice}() will notice this